Producing immunity
A vaccine introduces antigens associated with a pathogen into the body. The antigens stimulate a specific immune response, including production of specific antibodies by plasma cells.
Vaccines may supply the relevant antigen in different ways:
Weakened pathogen
The vaccine may contain a weakened form of the pathogen carrying its antigens.
Antigen
The vaccine may contain antigenic material from the pathogen.
Genetic material
The vaccine may contain genetic material that codes for the pathogen antigen.
Memory cells and later protection
Vaccination produces active immunity because the person's own immune system responds to the antigen. As part of this response, memory cells are formed.
- Vaccine antigens enter the body.
- A primary specific immune response occurs.
- Plasma cells produce specific antibodies.
- Memory cells remain after the initial response.
- Later exposure to the same antigen produces a faster and stronger secondary response.
The secondary response can remove the pathogen before the infection develops sufficiently for symptoms to appear.
Exam Tip: When explaining how vaccination protects someone later, do not stop at “antibodies are made”. Link vaccination → primary response → memory-cell formation → faster, stronger secondary response on later exposure.